The present invention relates to a series of new 6-(substituted phenyl)-4,5-dihydro-2H-pyridazin-3-one derivatives and to their use as agricultural fungicides.
A number of pyridazinone derivatives is known to have fungicidal activity. For example, those derivatives disclosed in United Kingdom Patent Specification No. 1,533,010, of which the most relevant may be represented by the formula: ##STR2## (in which R.sup.a may represent a hydrogen atom, a hydroxy group or an acyloxy group, R.sup.b and R.sup.d both represent halogen atoms or one represents a halogen atom and the other represents a hydrogen atom, and R.sup.c represents, inter alia, a hydrogen or halogen atom or an alkyl or alkoxy group) have been found to be effective against a wide range of pathogenic fungi whilst not exhibiting any phytotoxicity, when employed at effective doses.
Rather similar compounds, but having a substituent at the 2-nitrogen atom of the pyridazinone system are disclosed in European Patent Publication No. 72238, again having good fungidical activity.
Moreover, closer prior art, in that it has a substituent at the 4-position of the pyridazinone system, is 4-hydroxy-6-phenyl-4,5-dihydro-2H-pyridazin-3-one, which is disclosed in Japanese Patent Application Kokai No. 145685/79 as an intermediate in the preparation of various herbicidal compounds. Japanese Patent Application Kokai No. 8016/83 discloses various 6-(substituted phenyl)-4,5-dihydro-2H-pyridazin-3-one derivatives which may have a variety of substituents, including alkoxy groups, on the pyridazinone system; the substituents on the phenyl moiety, however, differ substantially from those in the present invention and the only specific compound having an alkoxy group (specifically an ethoxy group) on the pyridazinone system differs from the compounds of the present invention in that the substituted phenyl group of the 6-position is replaced by a tetrahydroquinazoline system. The activity described for these latter compounds is said to be a cardiac activity. No fungicidal activity is disclosed for any of the compounds of Japanese Patent Applications Kokai No. 145685/79 and No. 8016/83.